At the moment we support image uploads (png, jpg and gifs) and video embeds. Dedicated file attachments (such as pdf, epub, etc.) are not supported currently. For now we suggest linking to files hosting on your favourite cloud provider, this will work just as efficiently and maybe even better.
Why don't we have better support for attachments right now?
File uploads and PDF annotation was one of our goals with the original MVP when we started building Supernotes; so you could create notecards alongside your PDF. Although we quickly realised building a really good PDF annotator on the web is as challenging as building a really good note-taking experience – and often is easier and quicker to quickly add a cloud file link – so we ended up only focusing on note-taking and knowledge management.
We’d still like to add this, but feel like integrating with other tools and cloud file managers that specialise in PDF, Word, Powerpoint, or EPUB annotation is the best path forward for us at the moment.